The present invention relates to a system for high volume, accurate cutting of both hard and soft materials using a fluid jet cutting device. In particular, the present invention is directed toward a controlled cutting system having omnidirectional capabilities using water as the cutting agent.
The prior art is replete with devices and methods using high velocity liquid jets. Generally, as summarized in Machine Design, Feb. 22, 1973, pages 89-93, these techniques involve pressurizing a working fluid which is ejected using a high velocity discharge nozzle. U.S. Pat. Nos. 2,985,050 and 3,212,378 are representative of these prior art devices. The lack of success of these devices is attributed to the problem of dispersion of the working fluid upon ejection from the nozzle resulting in poor or irregular penetration for cutting along the prescribed path. Additionally, the work surface tends to become wetted and accordingly, in applications where depth of penetration, regularity of cut or absence of wetting become factors, these prior art devices are not suitable. Generally, hard materials such as ceramics, metals and lumber have been the subjects of interest for these prior art devices. U.S. Pat. No. 2,881,503 is also typical of this class of liquid cutters.
U.S. Pat. No. 2,006,499 demonstrates the converse, cutting of thin soft materials like paper sheets by low velocity jets in a environment where wetting is not a problem either because the material is already wet or because the thin sections of the cut will dry by evaporation very easily.
Attempts to introduce additives into the liquid to either reinforce the cut or shape the fluid to prevent dispersion have been attempted in the prior art as means of overcoming the problem of wetting in high velocity systems. U.S. Pat. No. 3,136,649 shows the use of a reinforcing material, such as a hardenable resin, to support the edges of the cut in a perforating system and U.S. Pat. No. 3,524,367 adds a long chain polymer to the fluid to improve cohesiveness and minimize dispersion of the fluid upon exiting from the jet. A variation is shown in U.S. Pat. No. 3,532,014 where the cutting rate of the fluid is optimized to volatize the retained fluid in the edges of the cut by heating due to frictional engagement of the material and the liquid jet. Such a system, while providing a solution to the problem of wetting, results in lower cutting rates and an inability to cut multiple layers of material.
For these reasons, high velocity liquid jet cutting of materials, especially soft goods such as fabrics has not been commercially used. Cutting techniques have continued to be centered around knife or die cutting. These systems continue to be wasteful of material and are not omnidirectional cutters thereby giving rise to the problem of maintaining proper blade angle. Likewise, the more exotic ideas such as laser cutting, while being omnidirectional in cutting, are restricted to a few well defined applications. Lasers, for example, are not suitable for cutting multiple layers because the heat associated with the cutting operation tends to bond the layers together. Hence, the prior art has failed to achieve a workable commercially successful omnidirectional cutting system for both hard or soft materials.
The prior art has generally used solid cutting tables as the only viable means of material support and the problem of wetting is obviously not solved by such equipment. The problem of material handling is also a function of the type of cutting table employed and the general lack of success in the exploitation of liquid cutters for all but the roughest cutting operations has precluded refinement of material handling techniques.